As a component of streamflow, baseflow is critical for regulating seasonal distribution of river flows and stabilizing water supplies. Water resources in the arid area of Northwest China are mainly from multiple catchments in the alpine that could be influenced by varieties of climatic, land cover, soil and geological factors. While numerous studies have been done on streamflow, systematic analysis of baseflow in the alpine river systems is scare. Based on historical daily streamflow data and the automated digital filter method of baseflow separation, this study investigated characteristics of hydrographs of overland flow, streamflow and baseflow of river systems fed by rainfall, snowmelt, glacier melt or mixtures of these. This study also calculated the recession constants and baseflow indices of 65 river systems. While the recession constant was 0.0034–0.0728 with a mean of 0.018, the baseflow index was 0.27–0.79 with a mean of 0.57. Further, Spearman’s correlation analysis showed that the baseflow index was significantly correlated with catchment climatic factors (e.g., precipitation and temperature), topographic factors (e.g., elevation and slope) and aquifer properties represented by the recession constant. Multiple regression analysis indicated that the factors explained 65% of the variability of baseflow index in the study area.

The change in natural runoff is highly relevant to total river flow dispatch and water resource utilization in the Yellow River Basin (YRB). Based on the annual mean temperature and total precipitation records from 70 meteorological stations from 1961–2020, the impact of climate change on the natural runoff of the YRB is investigated using the Mann-Kendall (M-K) test and Bivariate Wavelet analysis methods. Results show that the annual mean temperature over the YRB increased by 0.33 °C decade⁻¹ during 1961–2020, with a warming rate of more than 0.40 °C decade⁻¹ observed in its northern part. The annual total precipitation increases by 10–20 mm decade⁻¹ in the northwest YRB, while it decreases by 20–30 mm decade⁻¹ in the southeast YRB. The result of the M-K test shows abrupt variations in temperature and natural runoff, especially in the 1980s and 1990s. The decrease in natural runoff is closely tied to the increase (decrease) in temperature (precipitation), especially for the period 1993–2020. The bivariate wavelet coherence analysis further suggests that the decrease in the natural runoff, which has persisted over the past 60 years, is primarily driven by precipitation reduction rather than regional warming. In the stage of rapid warming, the inter-decadal influence of precipitation on natural runoff gradually changes to the influence of inter-annual fluctuation. The finding contributes to providing an important scientific basis for evaluating the optimal allocation of water resources in arid and semi-arid areas against the background of climate change.

The alluvial plain in the middle and lower reaches of the Yellow River is an important agricultural production base that affects groundwater quality. Groundwater quality in the region is related to the residential and production uses of water by local residents. Samples of shallow groundwater and river water were collected from the right bank of the middle and lower reaches of the Yellow River to determine the evolution and causes of hydrochemical characteristics, and the relationship between the hydrochemical evolution of river water and groundwater was explored. The results showed that the shallow groundwater in the area received lateral recharge from the Yellow River water. The closer to the Yellow River the groundwater was, the higher the SO₄²⁻, Cl⁻, and Na⁺ concentrations and the lower the HCO₃⁻ and Mg²⁺ concentrations were. Agriculture and aquaculture has influenced and complicated the hydrochemical types of shallow groundwater in recent decades. The groundwater in the area was jointly affected by water–rock interactions and evaporation concentrations; a strong cation exchange effect was detected. Arsenic exceeded the limit in some shallow groundwater, which was mainly distributed in the Yellow River alluvial plain and caused by the reductive sedimentary environment of the Yellow River alluvial plain. The “three nitrogen”, NH₄⁺-N, NO₂⁻-N, and NO₃⁻-N, demonstrated sporadic local excesses in shallow groundwater, which were related to human activities, such as aquaculture.

Desert terminal lakes are important signals to discern ecological degradation crises, particularly in arid areas where an artificial project of ecological water diversion has designated a quota of river water to prevent lake body shrinkage and protect the ecosystem. Knowledge of the minimum ecological water demand (EWD) is thus necessary to ensure the basic health of lake ecosystems. This study analyzed the spatiotemporal evolution of water boundaries using Landsat satellites data via remote sensing technology from 2002 to 2017 in East Juyan Lake, an inland desert terminal lake of the Heihe River in northwest China. The minimum lake water demand was determined using two estimation methods: the lake-evaporation-oriented EWD method and the minimum water level method. In the latter method, both lake topography (using water-level area curves) and biological survival demands (using bighead carps as indicators) were considered to derive the minimum lake EWD. Water diversion to the lake over the past 15 years has increased the lake’s area, but there are still marked intra-annual seasonal variations. The annual minimum lake water demand was suggested to be 54 × 10⁶ m³/year by comparing the different methods; however, it was not satisfied, and the lake survival was endangered when the occurrence frequency of the annual runoff in the Zhengyixia hydrological station exceeded 65%. This study offered promising directions for inland lake water resource management.

Affected by global climate change and rapid socio-economic development, China faces serious water security issues, especially in terms of water shortages, flood disasters, and water-related ecological and environmental problems

Affected by global climate change and rapid socio-economic development, China, along with many other countries worldwide, faces a series of water security issues, such as water shortages, flood disasters, and water-related ecological and environmental problems